Plant thinning apparatus



Sept 24, 1968 J. TSCHUDY, JR

PLANT THINNING APPARATUS 7 Sheets-Sheet l Filed May 4, 1967 I NVENTOR. JAY 75cm/ Y, de.

Sept. 24, 1968 J. TSCHUDY, JR

PLANT THINNING APPARATUS 7 Sheets-Sheet 2 Filed May 4, 1967 f6 im \\4\ A WA INVENTOR. J4 Y 750A/up Y, de. BY

A TTORNEY Sept. 24, 17968 .1. TSCHUDY, JR 3,402,507

PLANT THINNING APPARATUS Filed May 4, 1967 7 Sheets-Sheet 3 www L J TTQHVEY Sept. 24, 1968 l 1. TSCHUDY, JR

PLANT THINNING APPARAUS 7 Sheets-Sheet 4 Filed May 4, 1967 mvENTo /4y 75ml/00x Je.

arman/'EY 7 Sheets-Sheet 5 Sept, 24, 1968 1. TscHUDY, JR

PLANT THINNING APPARATUS Filed May 4, 1967 Sept. 24, 196s J- TSCHUDYy JR 3,402,507

PLANT THINNING APPARATUS 'Filed May 4, 1967 7 sheets-,sheet 7 for l a nl@ ummm INVENTOR.

@im 55M United States Patent O" 3,402,507 PLANT THINNING APPARATUS Jay Tschudy, Jr., Shawnee Mission, Kans., assigner to Precision Agricultural Machinery Company, Phoenix, Ariz., a corporation of Arizona VContinuation-in part of application Ser. No. 518,131, Jan. 3, 1966. This application May 4, 1967, Ser. No. 636,068

.. Claims. (Cl. 471.43)

ABSTRACT OF DISCLGSURE A plant thinning apparatus particularly directed to mechanism for selectively and automatically thinning and removing certain longitudinally spaced plants along a plant row to give'desired growth room between the plants operated by sensing elements contacting the plants in the row.

Cross-references to related applications This application is a continuation-in-part application or application Ser. No. 518,131, tiled Jan. 3, 196.6, now abandoned, of Jay Tschudy, Jr. for Plant Thinning Apparatus.

Background of the invention (l) The eld of this invention lies in agricultural machinery, and is particularly directed to a method and apparatus for automatically and selectively thinning plants from a plant row by sensing the location of plants growing in the plant row. e

,(2) IOne of the possible limitations on the use of precision planting of row crops where the seeds are planted at the precise spacing interval desired in the ultimate crop stand is that most seeds do not have a 100% germination. Where single seeds are planted at the ultimately desired spacing intervals and less than 100% germination is achieved, the row contains a lower crop stand than required to achieve a maximum economic realization from the field. At the present time it is accepted practice to plant seeds at closer spacing than ultimately desired and subsequently thinning the row after the majority of the seeds have sprouted. The present practice either necessitates the use of expensive hand labor or the use of mechanical thinning equipment which cannot discriminate as to which ofV the surplus plants should be thinned. In any event, compromises are made and the full economic realization of the iield is not achieved.

Summary of thepinvention The object of `this invention is to provide a sensory type plant thinning apparatus which is responsive to the actual presence and spacing of the plants to be controlled.

Another object is to provide a plant thinning device which is applicable to any crop which is thinned to one plant per hill along a plant row.

Another object is to provide a plant thinner particularly adapted to operate upon row crops such as sugar beets, cottonplants and the like.

It is also an object to provide a plant thinning apparatus including a memory unit that gives the implement the ability to :not only discriminate between friendly plants and weeds but as in the case of row crop such as beets, it retains a higher numberv of desirable plants than in former mechanisms of lthis type.

In instances where the seedlings in the plant row are accurately positioned at a predetermined spacing it is practicable with the instant machine to thin at a later date than heretofore possible under such planting conditions.

It is a further object to provide a plant thinning apice paratus which may be used at a later time or extension of the early growing season to give the grower the opportunity to work with the naturally stronger plants.

In certain instances it is an object of this invention to utilize chemical thinning processes.

It is an object to provide a plant thinning device of the sensory type which only under rare circumstances will be fooled by an unfriendly plant or weed.

It is an object of this invention to provide a chemical thinner of the sensory type which can be used in connection with plastic mulched crops along a plant row. The device of the instant invention is preferably to be used with a precision planted row which contemplates planting to a final stand where one plant to the hill is provided while still taking into consideration the realities of nature which will not permit such practice at the present time. The environmental planting system can be Safely utilized when twice the desired number of seeds are planted as an insurance factor.

In the instant invention as outlined above it is found suliiciently safe even to permit the use of pelletized seed Iwhich will greatly accelerate the acceptance of the apparatus and system where high cash value vegetable crops are to be controlled.

And it is also an object to provide an apparatus to selectively destroy particular plants in a plant row by an Brief description of the drawings FIG. l is `a side elevation of a sensory type thinner utilizing a mechanical plant removal element.

FIG. 2 is an enlarged section on the line 2-2 of FIG. l.

FIG. 3 is a diagrammatic side elevation of a sensory type plant thinning apparatus utilizing a chemical thinning process adapted to the fact that the plant does not die immediately when sprayed chemically.

FIG. 4 is an enlarged view of an especially -constructed circuit interruptor for the apparatus of FIG. 3.

FIG. 5 is a diagrammatic side elevation of still another modication of the control mechanism for the apparatus of FIG. 3.

FIG. 6 is an operation diagram of the apparatus shown in FIG. 5.

FIG. 7 illustrates the action of the thinning apparatus of FIGS. 1, 3 and 5.

FIG. -8 is a side elevation of another form of a sensory type thinner utilizing a mechanical plant chopper element.

FIG. 9 is a front elevation of the apparatus shown in FIG. 8.

FIG. 10 is an enlarged circuit diagram for a thinner apparatus essentially similar to that illustrated in FIGS. 8 and 9, but containing four mechanical chopper elements.

FIG. 1l is a thinning pattern diagram.

FIG. 12 is a density selection range diagram.

FIG. 13 is a density position thinner circuit diagram.

FIG. 14 is a side elevation of a sensory type thinner utilizing a -rotary solenoid actuated plant chopper element.

FIG. 15 is a front elevation of the apparatus shown in FIG. 14.

Description of the preferred embodiment In the specific case of growing sugar beets, for eX- ample, the seeds are planted at precise spaced intervals of one-half the plant spacing ultimately desired. vBy way of example, if it is determined that the ideal spacing in a pa-rticular iield is 10 inches, single seeds would be planted 5 inches apart, such as by the use of apparatus covered in Patents 3,154,031, 3,154,032 and 3,175,523, but this is not essential for the method and apparatus herein contemplated. Any planting method can be used, including hand planting, provided only that the seeds are planted at precise preselected spacing, in this instance substantially 5 inches apart.

After planting, the plant row will be permitted to germinate and after the sprouting of the seeds is complete, a thinning machine will -be run along the plant row 10 to cut out or otherwise destroy selected plants 11 which are considered to lbe surplus. The apparatus, FIGS, 1 and 2, will consist of a machine using three sensing elements 12, 13 and 14 which are mounted on a suitable sled 15 and will run immediately above ground level 16 and sen-se the germinated plants. The sensor elements will lbe spaced at precise distances 17 from each other which will correspond to the distance 18 between the planted seeds, in the case of sugar beets thus being substantially 5 inches.

Each of the sensors 12, 13 and 14 are connected to actuate normally open limit switches 19, 20 and 21 which are connected in series by leads 22 and 23, and connected at one end to a suitable power` supply lead 24 and at the other end through a lead 25 connected to one power input terminal 26 of a thinning wheel actuator motor 27 suitably mounted by a bracket 28 on the sled 15. The other terminal 29 of the actuator motor 27 is connected to the other power supply lead 30.

Fixed on the output shaft 31 of the actuator motor 27 is the hub 32 of the plant thinning wheel 33 from which radiate a series of spokes 34 terminating in thinning spades 35 adapted to move laterally of the plant row 10 upon intermittent rotation of the thinning wheel 33 by appropriately energizing the actuator motor 27. The machine will take no action until it senses three germinated plants that lie in a row 10 and are substantially 5 inches apart. When this condition prevails, the three sensing elements 12, 13 and 14 acting together, will close the circuit and the middle 36 of the three plants 11 will be destroyed as the wheel 33 which is activated by the circuit that is closed by limit switches 19-20-21 having all three of the sensing elements read the presence of a plant at the same time, is rotated and a thinning spade destroys the plant 36. If desired, the plant destroying means can be a ame.

In the embodiment of the invention illustrated in FIGS. 1 and 2, the plant destroying means is a rotary spade which physically destroys the undesired plants. The plant destroying means employed in the invention may be of any type which will electively kill the undesired plants and may be chemical, electrical or mechanical in nature. It is also possible to direct a flame against the undesired plant to destroy it. If the plant destroying means employed does not actually remove the plant at the time of destruction, means must be provided in the control circuitry so that the apparatus will treat the undesired plant as if it were destroyed so as not to erroneously sense the plant which will ultimately die, as being a part of the permanent stand in the field.

In its broader aspect, the apparatus can be used to thin any desired plant of a series which have sprouted at pre-set distances from each other. For example, in the case of lettuce, two sensing elements can be used to eliminate one undesired sprouted plant. In other instances, if it were decided that three plants in a row could be tolerated but not four, four sensing elements could be used to destroy the undesired fourth plant. In most, but not all instances, the equipment used will contain one more sensing element than the number of plants that can be tolerated at the spacing interval at which the seeds are planted in the plant row. Where an extra sensing element is not used, a signal accumulator or equivalent element must be utilized.

An arrangement of the chemical thinner of FIGS. 3

Cil

and 4 is utilized in view of the fact that the plant 36 does not die immediately when sprayed and remains in the eld to be sensed and to actuate the subsequent spraying of additional adjacent plants. To overcome this problem a fourth sensing element 40 is provided which is not tied in directly with the three sensing elements 12-13-14 which actuate the spray nozzle 37, but merely trips an actuator 41 each time it contacts a plant 11 in the Plant row 10. A supply line 38 provides plant destroying material for the spray nozzle 37.

The sensor 40 of the actautor 41 causes the actuator to intermittently actuate the circuit interruptor 43 which is connected to the shaft 44 so as to each time move the contact arm 45, FIG. 6, either to a connected position 46 of leads 25 and 29a with power lead 30 through lead 47 or to disconnected position 48 of these leads 25 and 47, to thus energize or deenergize the series circuit through the limit switches 19-20-21 to activate or deactivate the functions of the sensors 12-13-14, so that the sensing element 40 of the actuator can over-ride the three sensing elements for the spray nozzle 37. By this arrangement, before a plant will be sprayed the three sensing elements 12-13-14 must be closed and the actuator 41 must have moved the circuit interruptor to a connected position 46 before solenoid valve 39 is opened and any plant will be sprayed. The distance 40a between sensor 40 and the sensor 14 must be less than the distance 17 between the sensors 12-13 and 13-14. Ordinarily the distance of spacing 40a is one-half the distance 17. This modication will assure that only the plants to be thinned are actually sprayed.

Still another embodiment of this invention, FIGS. 5 and 6 is to thin, for example, sugar beets 11 by spraying a selected plant 11 when three plants in a row sprout on substantially 5 inch centers 18. The device is` similar to the four sensing element device shown in FIGS. 3 and 4 but two of the sensing elements have been eliminated as their function is replaced by a memory unit actuator 49.

This arrangement operates as follows: As the sled 15 moves down the crop row 10 and sensing element 50 reads a plant 11, the memory unit actuator 49 remains in position 51 and does not open the solenoid valve 39. The same situation prevails if sensing element 53 reads a plant. If sensing elements 53 and 50 both read a plant, the memory unit actutaor 49 is moved to position 54, but the solenoid 39 is not actuated. The next action of memory unit actuator 39 depends upon the next signals received from sensing elements 50 and/or 53. If the next contact with plants involves both units 53 and 50, the memory unit actuator 49 moves to position 55, the solenoid 39 is energized to open position and the third plant 36 is sprayed. After the solenoid 39 has been energized and the third plant 36 has been sprayed, the memory unit actuator 49 returns to position 51. Alternatively, if after the memory unit actuator 49 is moved to position 54, the next contact with the plants involves only sensing element 53 or 50, the memory unit actuator 49 is returned to position 51.

A source of power such as a battery 56 is connected to the memory -actuator 49 unit so that the normally open limit switches 57 and 58 of sensors 50 and 53, connected thereto by leads 59, may control the functions of the actuator 49 as described. The solenoid valve 39 for the nozzle 37 is connected by suitable leads 50 through a suitable time delay relay 61 through leads 62 to the actuator 49, the delay relay serving to control the exact travel position of nozzle 37 to plant 36 and moment of spray from the nozzle 37 during the forward movement of the sled 15 along the plant row 10 so as to be sure the sprayed material is properly centered on and fully covers the plant to be eliminated. The apparatus of this invention can be adapted to readily give the grower a total count of the seeds that have germinated in a field, the number of the germinated plants that have been thinned and from these two figures the plant population of the eld. This information can be of substantial value to the grower in evaluating the eifectiveness of new planting practices, e.g., the etliciency of experimental fungicides, nematocides and the like, and in accurately predicting the yield of any given eld. To obtain such information, a first counting device can be activated by one of the sensing elements when its senses the presence of a plant and a second counting device can be a-ctivated by the signal fed to activate the plant destroying mechamsm.

The apparatus of the invention can be built to destroy any desired plants of those sensed. As illustrated in FIGS. 1 and 3 the middle of the 3 sensed plants is destroyed. The embodiment illustrated in FIG. 5 destroys the last (in the direction of travel of the sled) of the three sensed plants. The embodiment illustrated in FIGS. 8, 9 and 10 destroy the lirst (in the direction of travel of the sled) of the three sensed plants.

FIG. 7 illustrates the action of the apparatus of either of FIGS. 1, 3 and 5 in thinning a typical crop such as sugar beets which are planted on 5 inch centers and it is desired to thin the crop so that no 3 adjacent plants are permitted to grow on 5 inch centers. As illustrated with the first 14 seeds planted in a row, 4 seeds have failed to germinate as designated by an X at plant positions at d, z' and j. The germinated plants are illustrated as open circles. It the row were not thinned, the plants at plant positions e, f, g and ht and also at k, l, m and n would be stunted because of overcrowding. After the tield is thinned, the plants at f and I have been removed and more favorable growing conditions will be obtained for plants e, g, h, k, m and n.

In the arrangement shown in FIGS. 8 through 13 inclusive, there is provided a plant thinning machine having a frame 60- mounted on a suitable sled 61 which is pulled along the ground level 16. Two sensing devices 62 and `63 are mounted on the frame 60 behind the thinning mechanism indicated generally at 64 which may take the form of a swinging double edge hoe element 65 having the oppositely disposed thinning blades 66 mounted to swing on suitable pivot pins 67 carried on the frame 60 about longitudinally disposed horizontal axes 68 relative to the plant -rows 10. Pivotally connected by pins 70 to the outer ends of the integral actuating levers 69 of the swinging hoe elements 65 are the piston rode 71 of suit- |able tluid pressure cylinders 72 carried on the frame 60. A suitable source of iluid pressure is transmitted from the pressure supply line 73 connected to the electrically operated reversing valves 74 operable to control the cylinders 72 and the laterally swinging plant chopping and thinning blades 66.

The normally open contacts 78 of sensing elements 62 and `63, FIG. 8, are connected in series by leads 75, 76 and 77 with one terminal 79 of a control valve 74 and ground, while a source of electrical energy `80 is connected -between the other terminal 81 and ground by the leads 82 and 83.

In the circuitry shown in FIG. 10, four rows of plants are to be treated simultaneously. The apparatus is wired with a selector switch 84 having the operating handle 85. Two circuits A land B are available. With the A circuit selected, both sensing elements 62 and 63 lare part of the circuit 75, selector switch 84, 75, 76 and 77. Under these conditions sensing elements 62 and `63 must necessarily contact two consecutive plants 11 before the thinning mechanism `64 can be actuated to chop out a plant. Therefore, if only a single plant 11 is sensed, nothing will happen. When two plants are sensed, with a skip at the next planted position (in the direction of sled travel) the thinning blade 66 is actuated, but no plant is removed. If three consecutive plants 11 are encountered, the leading or forward plant is removed. The A circuitry establishes the pattern shown in FIG. 11, A.

In the arrangement shown in FIGS. 14 `and 15, there is provided a plant thinning machine having a frame 87 mounted on a suitable sled -88 which is pulled along the ground level 16. Two sensing devices 89` and 90 are mounted on the frame 87 behind the thinning mechanism indicated generally `at 91 which may take the form of a swinging double edge hoe element 92 having the oppositely disposed thinning blades 93 mounted to Swing on rock shaft 94 of 1a rotary solenoid 95 carried on the frame 87 for swinging about longitudinally disposed horizontal axes 96 relative to the plant rows 10. The arm 97 of the hoe element 92 is interconnected by a tension spring 98 which normally yieldingly holds the hoe element to one side of the plant row 10. Whenever the solenoid is energized, the hoe element swings to the other side of the row, the spring 98 returning the hoe element to the opposite side when the solenoid is deenergized.

A suitable source of electrical energy 99 has one lead 100 connected to the solenoid 95 and its other lead connected to ground. The other lead 101 is connected to the lixed contact 102 of sensing device 89. The movable contact 103 of the sensing device 89 is connected by lead 104 to ground while the iixed contact 105 is also connected to ground lead 104. The movable conta-ct 106 is connected by a lead 107 to ground, contacts 102-103 and 105-106 being normally open. A control circuit such as shown in FIG. l0 may be utilized to actuate and deenergize the rotary solenoids 95 in the manner that the control valves 74 of FIGS. 8 and 9 are operated.

When the handle 85 of selector switch 84 is adjusted for B circuitry, the rear sensing element 63 is bypassed in the circuit 75, selector switch 84, 86 So that it is necessary to encounter one plant 11 in order to actuate the hoe 65. B circuitry establishes the pattern shown in FIG. l1, B.

In summary, when four rows of thinners are utilized as shown in FIG. l0, it will be possible to establish five dilerent thinning patterns on any given emergence pattern, or more important, ve different ranges of end plant population. It will be possible for the grower to select such setting as will best match the production potential of a particular soil, stronger soils being able to support a denser stand than can be maintained by weak soils.

FIG. l2 shows the plant populations that can be obtained using the Vapparatus illustrated in FIG. 11. In the experiment illustrated 78,369 seeds per acre are planted on centers 4" apart in rows spaced 40 apart. With 60% germination the iield population would be as shown in which the circles represent a germinated plant and the Xs represent skips. The plants which are selectively destroyed are represented by the filled in or black circles. When all of the thinners are operated on the capital A circuitry, the plant population is reduced to 38,218 plants per acre. When all of the thinners are operated on the capital B circuitry, the plant population is reduced to 23,519 plants per acre. The plant population with the above are shown in FIG. l2. FIG. 13 illustrates the combination of circuitry used to obtain the plant population shown in FIG. 12.

While the apparatus herein disclosed and described constitutes a preferred form of the invention, it is also to be understood that the apparatus is capable of mechanical alteration without departing from the spirit of the invention and that such mechanical arrangement and commerci-al adaptation as fall within the scope of the appendent claims are intended to be included herein:

I claim:

1. A plant thinning apparatus comprising in combination:

(a) a frame arranged to be moved along a plant row,

(b) plant sensing elements mounted on said frame in longitudinally spaced positions relative to the plant row to simultaneously sense a plurality of substantially equally longitudinally spaced plants in the plant row to generate a signal when a preselected number of contiguous plants are present on preselected spaced centers along the plant row,

(c) -a plant thinning Wheel mounted on the frame for movement transversely to the direction of travel of the frame,

(d) a plurality of radially disposed circumferentially spaced spokes on said planting wheel,

(e) thinning spades fixed to the outer ends of said spokes, and

(f) means actuated by the signal received from the plant-sensing elements to intermittently rotate the plant thinning wheel;

said plant thinning wheel being mounted on said frame intermediate of the plant sensing elements so as to destroy one of the intermedi-ate plants sensed.

2. A plant thinning apparatus comprising in combination:

(a) a frame arranged to be moved along a plant row,

(b) plant sensing elements mounted on said frame in longitudinally spaced positions relative to the plant row to simultaneously sense a plurality of substantially equally longitudinally spaced plants in the plant row to generate a signal when a preselected number of contiguous plants are present on preselected spaced centers along the plant row, said plant sensing elements comprising at least two sensing elements which are spaced apart longitudinally the same distance as the longitudinal spacing of the seeds in a plant row where planted, said sensing elements being series connected so that a signal is generated only when the sensing elements simultaneously sense a pair of plants,

(c) means on said frame actuable to destroy a particular plant of the plurality sensed by said plant sensing elements,

(d) means to actuate the plant destroying means when signal is simultaneously received from a plurality of said plant sensing longitudinally spaced sensing elements, and

(e) an over-riding sensing element mounted longitudinally forward of the first of the plant-sensing elements and being spaced therefrom less than the distance between the plant-sensing elements and being adapted to alternately open -and close a switch as it senses a plant;

said apparatus being further characterized in that the switch controlled by the over-riding sensing element is connected in series with the plant-sensing elements and the means to actuate the plant destroying means.

3. A plant thinning apparatus comprising in cornbin-ation:

(a) a frame arranged to be moved along a plant row,

(b) plant sensing elements mounted on said frame in longitudinally spaced positions relative to the plant row to simultaneously sense a plurality of substantially equally longitudinally spaced plants in the plant row to generate a signal when a preselected number of contiguous plants are present on preselected spaced centers along the plant row,

(c) a swingable double-edge hoe mounted to be swung transversely to and through the soil of the plant row, and

(d) means to actuate the swingable hoe when a signal is simultaneously received from a plurality of said plant sensing longitudinally spaced sensing elements;

said hoe being mounted immediately forward of the plant sensing elements and being positioned so that, when actuated and swung through the soil, it contacts the soil at a distance from the plant sensed by the lead plant sensing element that is equal to the minimum spacing between plants in the plant row.

4. The plant thinning apparatus of claim 3 in which the swingable double-edge hoe is mounted on a shaft to be swung transversely to the plant row and the said shaft is swung by a rotary solenoid which swings the hoe through the soil and then returns the hoe to its initial position.

5. The plant thinning apparatus of claim 3 which includes:

(a) a frame arranged to be moved along a plant row,

(b) plant sensing elements mounted on said frame in longitudinally spaced positions relative to the plant row to simultaneously sense a plurality of substantially equally longitudinally spaced plants in the plant row to generate a signal when a preselected number of contiguous plants are present on preselected spaced centers along the plant row,

(c) means on said frame actuable to destroy a particular plant of the plurality sensed by said plant sensing elements,

(d) means to actuate the plant destroying means when a signal is simultaneously received from a plurality of said plant sensing longitudinally spaced sensing elements, and

(e) a rst counting element which is actuated by one of the plant-sensing elements to count each plant as the apparatus is moved along a plant row, and a second counting element which registers each time the plant destroying means is actuated to destroy a plant.

6. A plant thinning apparatus comprising in combination:

(a) a frame arranged to be moved along a plant row,

(b) plant sensing elements mounted on said frame in longitudinally spaced positions relative to the plant row to simultaneously sense a plurality of substantially equally longitudinally spaced plants in the plant row to generate a signal when a preselected number of contiguous plants are present on preselected spaced centers along the plant row, said plant sensing elements comprising at least two sensing elements which are spaced apart longitudinally the same distance as the seeds in a plant row were planted, said sensing elements being connected so that a signal is generated only when said sensing elements simultaneously sense a plant,

(c) an over-riding sensing element mounted longitudinally forward of the rst of the plant-sensing elements and being spaced therefrom less than the distance between the plant-sensing elements and being adapted to alternately open and close a switch as it senses a plant,

(d) a plant destroying means comprising a liquid discharge nozzle adapted to spray a herbicide on the plant to be destroyed, and

(e) means to actuate the plant destroying means when a signal is simultaneously received from a plurality of said plant-sensing longitudinally spaced sensing elements;

said apparatus being further characterized in that the switch controlled by the over-riding sensing element is connected in series with the plant-sensing elements and the means to actuate the plant destroying means.

7. A plant thinning apparatus comprising in cornbination:

(a) a frame arranged to be moved along a plant row,

(b) plant sensing elements mounted on said frame in longitudinally spaced positions relative to the plant row to simultaneously sense a plurality of substantially equally longitudinally spaced plants in the plant row to generate a signal when a preselected number of contiguous plants are present on preselected spaced centers along the plant row,

(c) means on said frame actuable to destroy only a single particular plant of the plurality of plants sensed by said plant sensing elements, and

(d) means to actuate the plant destroying means when a signal is simultaneously received from a plurality of said plant sensing longitudinally spaced sensing elements.

8. The apparatus of claim 7 in which said means to destroy a plant is located on said frame intermediate the front and rear of said longitudinally spaced plant sensing elements.

9. A plant thinning apparatus comprising in combination:

(a) a frame yarranged to be moved along a plant row,

(b) plant sensing elements mounted on said frame in longitudinally spaced positions relative to the plant row to simultaneously sense a plurality of substantially equally longitudinally spaced plants in the plant row to generate a signal when a preselected number of contiguous plants are present on preselected spaced centers along the plant row,

(c) a plant thinning wheel mounted on the frame for movement transversly to the direction of travel of the fr-ame,

(d) a plurality of radially disposed circumferentially spaced spokes on said planting Wheel,

(e) thinning spaces fixed to the outer ends of said spokes, and

(f) means actuated by the signal received from the plant-sensing elements to intermittently rotate the plant thinning wheel;

said plant thinning Wheel being mounted immediately forward of the plant sensing elements (in the intended direction of travel) and being positioned so that, when actuated and rotated transversely to the direction of travel of the frame, the thinning spades carried thereby contact the soil at a distance from the plant sensed by the lead plant sensing element (in the intended direction of travel) that is equal to the minimum spacing between plants in the plant row.

10. A plant thinning apparatus comprising in combination:

(a) a frame arranged to be moved -along a plant row,

(b) plant sensing elements mounted on said frame in longitudinally spaced positions relative to the plant row to simultaneously sense a plurality of substantially equally longitudinally spaced plants in the plant row to generate a signal when a preselected number of contiguous plants are present on preselected spaced centers along the row,

(c) means on said frame actuable to act upon ya locus of the plant row occupied by an earlier planted seed and destroy any plant occupying said locus, and

(d) means to actuate the plant destroying means when a signal is simultaneously received from a plurality of said plant sensing longitudinally spaced sensing elements;

said plant destroying means being mounted immediately forward of the plant sensing elements (in the intended direction of travel) and being positioned so that, when actuated, it acts upon a locus of the plant row at a distance from the plant sensed by the lead plant sensing element (in the intended direction of travel) that is equal to the minimum spacing between plants in the plant row.

References Cited UNITED STATES PATENTS 1,303,789 5/1919 Janes 172-6 XR 2,507,001 5/ 1950 Ferte 172-6 2,592,689 4/1952 Hann 172-6 2,682,132 6/ 1954 Marihart 47-1 3,181,618 5/1965 Miller 172-6 FOREIGN PATENTS 900,280 7/ 1962 Great Britain.

ROBERT E. BAGWILL, Primary Examiner. 

